In the meantime, the property should not require a restart correct (set from script console)?
I'm not sure that setting the system property from the script console will work. The system property value is read once when the GitStatus Java class is initialized. I'm not sure if that is before or after system init hooks are processed by groovy.
With the run-jenkins.sh
script described in an earlier comment, I replaced the system property set from the command line with a system property set from the script console. The script console version did not disable the notifyCommit token even though the property is displayed in the system information page.
You'll need to use a command line property to set that value or the git plugin will need to be extended to read the notifyCommit property value more often. It currently reads it only once when the JVM starts.
I'm not able to duplicate the problem as described. Steps that I took while attempting to duplicate it include:
When I ran that curl command with the property set to the value disabled, the notifyCommit caused the repository to be polled and the job to be built.
I suspect that the system property is not being set from the Java command line, either because it is being set in the wrong location on the Java command line or is not being passed on the command line in a way that is detected by Jenkins. You can check if the property is set by opening the /manage/systemInfo URL and unhiding all the values. On my system, when the property is set, there is an entry that shows the value of that property.